Field of the Invention
This invention relates to a micrometer, in particular a fluid-tight electronic micrometer.
Electronic micrometers are known in which the measured distance is determined by an electronic system of measurement, for example a capacitive system, and is displayed on an electronic display, for example a liquid crystal display. Compared to conventional mechanical micrometers, these electronic micrometers have in particular the advantage of notably improved reading comfort as well as the possibility of storing and transferring the values measured.
These devices must be kept sufficiently clean in order to function, and are thus badly suited to operate in a humid environment or an environment subject to dust, or to splashing of lubricant or cutting oil. In particular, it is important to see to it that the capacitive electrodes of the measuring system remain free of any humidity.
U.S. Pat. No. 5,433,016 to Tachikake et al describes an electronic micrometer having different means for preventing the infiltration of water into certain portions of the micrometer. In particular, annular joints are provided to stop the infiltration of water along the screw. A tube made of a thermosetting shrinkable material protects certain mechanical elements, in particular the mechanism for adjusting the play between the screw and the sleeve. An opening through the casing allows the pressure inside the latter to be equalized with the external atmospheric pressure. Nothing is provided in the described device, however, to protect the capacitive electrodes, the electronic measuring circuit and the display or the threaded portion of the micrometric screw or of the sleeve from infiltration of water.
The patent publications JP-7-159102 and JP-6-194102 describe similar micrometers in which only part of the components are protected from humidity.